Large-format prints are viewed from farther away. Demanding 300 DPI at billboard size is unnecessary and can make files huge or impossible to output. The right resolution depends on viewing distance and product type.
Viewing distance and sharpness
The eye cannot resolve fine detail beyond a certain distance. A 3-foot sign viewed at 3 feet needs higher resolution than a 10-foot banner viewed at 10 feet. We use lower DPI for large-format because the viewer is farther away.
Typical large-format DPI
150 DPI at final size is common for vehicle graphics and indoor signage. 72–100 DPI is often acceptable for banners and billboards. Your printer will specify minimum resolution for each product.
Setting up your file
• Build at final output size (or scale proportionally).
• Use the DPI your printer specifies for that product and size.
• Do not scale up a low-res image; it will still look soft in print.
Common mistake
Sending a file built at 300 DPI for a 20-foot banner. File size explodes and may not run on the RIP. Or sending 72 DPI for a poster viewed at arm's length; it will look pixelated.